Preparation Of 3D Multi-component Composite Electrode Materials And Application In Flexible Solid Supercapacitors

Flexible solid-state supercapacitor（FSSC）is one of the most promising energy devices for wearable and portable electronics due to the advantages of high energy/power density,outstanding flexibility,good mutual compatibility and safety.However,the serious performance decay of the FSSC caused by the structure and shape deformation of the devices remains a crucial challenge.Therefore,the development and research of the flexible electrodes of FSSC are particularly important.The key challenge is the design and fabrication of the electrode.An excellent and stable electrode structure is the key factor for high performance and functional electrode.Three-dimensional heterogeneous porous nanostructures,with regular and orderly structure and a large number of mesoporous have many advantages.It can provide a very high specific surface area to expose more active sites for fast redox reaction,enhancing the generation and transport of electrons.Besides,the rich pore channels will accelerate the ionic transport of electrolyte,and the good structural stability can improve the mechanical stability of the electrode.Thus,flexible electrode materials have the a wide application potential.In this study,a three-dimensional nanowire array was prepared,as a three-dimensional skeleton,to construct a three-dimensional heterostructure by combining multiple materials.Through the synergistic effect between different materials,the overall performance of the electrode is improved to prepare an electrode material with high energy density,power density and long cycle stability,and a flexible solid-state supercapacitor was constructed.The main research work is as follows:（1）A stable three-dimensional nanostructure was constructed by fabricating Co₃O₄nanowire arrays on the substrate of Ni foam using a hydrothermal method.Based on this three-dimensional architecture,MnO₂ and PPy nanomaterials were grown on it in two different sequences using an electrochemical deposition method,and 3D Co₃O₄@MnO₂@PPy and Co₃O₄@PPy@MnO₂ multiple composite nanostructure electrode materials were prepared,respectively.The composite of different materials improves the electrochemical performance of the electrode,and different structural combinations show different performance.（2）3D Co₃O₄@MnO₂@PPy composite core-shell nanostructure was prepared by a one-step co-deposition method to form a composite shell of MnO₂ and PPy at the molecular level on the 3D Co₃O₄ nanowire array with a flexible carbon cloth substrate.MnO₂ with high theoretical specific capacitance and PPy with highly conductivity are uniformly doped at the molecular level,which produces a molecular coupling effect to increase the redox active sites of the electrode material.It fully activates the composite electrode material to participate in the reversible process of the redox reaction,enhancing the electron transfer efficiency of the composite shell and the overall electrochemical properties of the electrode material performance.（3）A symmetrical flexible solid-state supercapacitor was fabricated with 3D Co₃O₄@MnO₂-PPy composite core-shell nanostructured flexible electrode.The flexible-state solid supercapacitor achieves an energy density of 41.3 Wh kg^-1 and a power density of 4348W kg^-1.More importantly,the unique three-dimensional electrode structure beneficial to avoids structural collapse during bending,folding or twisting,and the capacitance does not change obviously under bending at various angles.The high capacitance retention of 93.0%after 1000 bending and twisting cycles are also achieved,indicating that it has a great potential application in wearable and portable electronics.